With the advent of semiconductor technology, microwave transistor manufacturers and other electronic system designers compromised some degree of power and high speed for the overriding economic and technological advantages of semiconductor technology. Two principal advantages of semiconductor technology are the small size and the ability to manufacture thousands of separate identical devices with few manufacturing process steps. With increasing power demands for electronic systems and the requirement that the systems operate at even higher frequencies, however, electronic component designers are reconsidering the construction of semiconductor devices. In particular, some designers are considering the possibility of incorporating the advantages of vacuum tube technology at microelectronics scale of semiconductor devices.
Attempts have been made to create an enclosed chamber having an emitter, a grid, and an anode constructed on a single silicon substrate using semiconductor process technology. The obvious advantages of this approach are cost effectiveness and use of the semiconductor process techniques and high volume output inherent in these methods. To date, however, these attempts have been unsuccessful. One noteworthy effort has been to establish within a silicon substrate an oxide base on which a high temperature metal is placed and an electrode is formed. For example, C.A. Spindt, et al., "Physical Properties of Thin-Film Field Emission Cathodes with Molybdenum Cones," J. App Physics, Vol. 47, No. 12 (Dec. 1976) describes a semiconductor process for producing a thin-film field emission cathode using semiconductor technology. Other more recent attempts have been successful in establishing a grid that may be used for a microelectronics triode or diode. However, as yet there have been no successful attempts to establish a vacuum microelectronics chamber comprising an emitter, a grid, and an anode for use as a vacuum microelectronics triode or diode. In particular, there have been no successful attempts to seal a vacuum within a microelectronics device of this type using solely semiconductor device fabrication techniques.
Those attempts which have successfully produced a cathode or emitter and even a grid use the oxide and high temperature metal combination already described. In fabricating the emitter and grid structures in these processes, it is necessary to remove the oxide. The oxide, however, can not be isotropically plasma-etched in a semiconductor fabrication process. It must be wet-etched in a heated wet-etch process. Significant problems associate with the removal of the oxide with a wet-etch process. For example, wet-etch material residue invariably will remain on the emitter and grid. Moreover, wet-etch processes that remove the oxide also remove the metal, even for high temperature refractory metals. Using the oxide and high temperature metal techniques, it has not yet been shown that a vacuum seal can be achieved.
Consequently, there is the need for a method for producing a vacuum microelectronics device such as a triode or diode that while incorporating the advantages of semiconductor process technology provides the improved power and speed advantages of vacuum tube technology.
There is the need for a method for producing a microelectronics device that successfully creates a vacuum seal chamber on a semiconductor substrate.
There is the further need for a method for producing a vacuum microelectronics device that avoids the residue problems and metal etch problems associated with known methods for producing an emitter and grid on a semiconductor substrate.
Furthermore, there is the need for a method for producing a vacuum microelectronics device that in a simple process produces multitudes of vacuum chambers comprising an emitter, a grid and an anode to form microelectronics triodes or diodes on a semiconductor substrate.